Charge correlations and transverse momenta observed in multifragmentation of 1 GeV/nucleon Au projectiles

We have investigated the fragmentation of $^{197}\mathrm{Au}$ projectiles at 0.85 to 1 GeV/nucleon in collisions with targets (${\mathrm{CH}}_{2}$${)}_{\mathit{n}}$, C, and Pb. Using plastic nuclear track detectors all projectile fragments with charge 6\ensuremath{\le}${\mathit{Z}}_{\mathit{F}}$\ensuremath{\le}77 produced in a collision were observed in coincidence. The combination of C and (${\mathrm{CH}}_{2}$${)}_{\mathit{n}}$ data allows us to extract the hydrogen component in measured distributions by the use of the statistical subtraction method. Our data show a target dependence of the multifragmentation process which indicates a nonequilibrated source of the fragments and/or the influence of the target nucleus on the relation between size and excitation energy of the spectator. In comparison to the prediction of the statistical model, the transverse momentum dispersions are enhanced with a dominant contribution by Coulomb repulsion between the fragments. Based on the sum of transverse momentum vectors of all fragments we conclude that multifragmentation is observed in collisions with a large momentum and energy transfer to the prefragment. Correlations in the azimuthal emission angles of the fragments are caused by mutual repulsion and momentum conservation. The idea that a liquid-gas phase transition of nuclear matter is the origin of multifragmentation is supported by our observations.